Problem: A young sumo wrestler goes on a special diet to gain weight. The variable $w$ models the wrestler's weight (in kilograms) after the wrestler has been on a special diet for $t$ months. $w=80+5.4t$ How much weight does the wrestler gain every $2$ months?
The rate of change of the equation is $5.4$ kilograms per month. To find the weight gain, we can multiply the rate of change by $2$, the number of months. $5.4\, \dfrac{\text{kilograms}}{\cancel{\text{month}}} \cdot 2\,\cancel{\text{months}}=10.8 \text{ kilograms}$ The wrestler gains $10.8$ kilograms every $2$ months.